So now your tribe and this hypothetical torturing tribe view each other as inferiors. You're "weak", and they're "cruel". Now what? Do you boycott and embargo trade with them? Do you go to war preemptively, or only after one of yours gets tortured by one of theirs? Perhaps you launch a propaganda campaign to depict them as mindless savages that revel in the pain of innocents? Maybe you single them out at the border, and loudly demand that they publicly pledge to not torture anybody while they are visiting your territory? That isn't likely to make them stop torturing.
I'm not seeing your point. An argument from morality only works for people who share your morals, a group that necessarily excludes those people who engage in torture. People who share your morality already don't torture. An argument regarding the efficacy of the technique is more likely to get a torturer to stop, whereas the moral argument only reinforces a pre-existing aversion. And thanks to cognitive dissonance, the longer someone has been torturing, the less likely they are to listen to anyone telling them that torture is wrong. If you reframe it as an evolution in effective interviewing technique based on recent scientific research, they have a psychological "out" that allows them to stop torturing without having to reframe themselves as a bad guy.